The present invention relates to a fluid flow sensor and a method of fabricating the same fabricated by a semiconductor process.
One type of a conventional thermal fluid flow sensor for use in detecting flow amount of air is disclosed in U.S. Pat. No. 5,404,753 (JP-A-6-50783). In this thermal fluid flow sensor, a thin film semiconductor flow detecting part and a bonding pad (conductor part) are provided on the same plane and separated from each other by a separation wall. As a result, it is not possible to reduce the planar size of the fluid flow sensor.
It is an object of the invention to provide a fluid flow sensor capable of reducing its planar size and a method of fabricating the same.
In one of preferred embodiments, a fluid flow sensor comprises a fluid flow sensor chip that includes a board and detecting portions formed on a first surface of the board for detecting a flow rate of fluid flowing above the first surface of the board. The fluid flow sensor chip further includes a substrate conductor portion electrically connected to the detecting portions and formed on a surface other than the first surface.
In fabricating the fluid flow sensor, thin film layers are formed above the first surface of the board, and a hollow cavity portion is formed by etching the board from the side of a second surface of the board opposite the first surface. A through hole is formed in the board where the hollow cavity portion is not formed. A conductor is formed on an inner wall face of the through hole to form a substrate conductor portion on the side of the second surface of the board.